Recycling & Waste Management
Adding value to waste
P
ackaged food waste is a valuable commodity and a rich source of material for anaero- bic digestion (AD) plants.
The main food stuff materials avail- able are packaged supermarket waste and kerbside collected kitchen waste which generally arrives in the dreaded biodegradable starch bags.
Starch bags pose their own problems to AD, if not removed they wrap around mixers, block pumps and screw conveyors and take up valuable space in the digesters. The bags
will not break down in the digesters as they require air to degrade (aerobic). Depending on the environmental conditions and thick- ness, starch bags will take from six weeks up to one year to totally degrade. Farmers are not so keen to spread digestate which include starch bags, because their fields initially gain the appearance of a landfill site prior to the bags decomposing. Starch bags are only made up of typically 15% starch the remainder is inorganic matter. There are a growing number of machines coming onto the market professing to be the
Packaged food waste is a rich source of material for anaerobic digestion plants if it can be separated from its bag. Here’s how Atritor’s Turbo Separator can help
solution to the depackaging problem. The majority of the depackaging equipment presently available, are based on hammer mills or shredding machinery which shred the pack- aged food waste before passing it through a squeezing process. Shredding reduces all the mate- rial to a similar size increasing the difficulty of separation at the next stage. The size of the screens fitted has a profound effect on the amount of packaging passing through with the
12 June 2012 Solids and Bulk Handling
www.solidsandbulk.co.uk
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